An xanthene dye, pyronine Y, was found to exhibit opposite fluorescence behaviors at different pH values in the presence of N,N’-bis(2- aminoethyl)-2,2’-biquinoline-4,4’-dicarboxamide-bridged bis(β-cyclodextrin)(2). That is, pyronine Y showed the quenched fluorescence in an acidic(pH 2.0) or a neutral(pH 7.2) environment, while the enhanced fluorescence in a basic environment(pH 12.0), with the addition of 2. Further studies by fluorescence titrations and 2D NMR indicated that different binding modes of positively charged and neutral PY molecules upon complexation with bis(β-cyclodextrin) 2 should be responsible for opposite fluorescence behaviors. This result may enable the biquinolino-bridged bis(β-cyclodextrin) as an efficient chemical sensor for the protonation and deprotonation of xanthene dyes.

采用荧光光谱滴定的方法测定了一系列联喹啉桥联双环糊精在磷酸缓冲溶液中(25℃，pH＝7.2)与几种染料客体分子形成化学计量比为1∶1的超分子配合物的稳定常数。结果表明，拥有刚性和大π电子体系的联喹啉桥联双环糊精比相应的联吡啶桥联双环糊精对三角形的RhB分子和线形的AR分子具有更强的分子键合能力。二维核磁的研究证实，桥联双环糊精对客体分子强的键合能力起源于在一个分子内两个环糊精单元的协同键合。桥联双环糊精对染料客体分子的选择键合能力从主-客体间的尺寸/形状匹配以及几种弱相互作用力的协同效应进行了讨论。

To investigate quantitatively the cooperative binding ability of β-cyclodextrin dimers, a series of bridged bis(β-cyclodextrin)s with 2,2′-diselenobis(benzoyl) spacer connected by different lengths of oligo(ethylenediamine)s(2-5) and their platinum(IV) complexes(6-9) have been synthesized and their inclusion complexation behavior with selected substrates, such as Acridine Red, Neutral Red, Brilliant Green, Rhodamine B, ammonium 8-anilino-1-naphthalenesulfonate, and 6-p-toluidino-2- naphthalenesulfonic acid, were investigated by means of ultraviolet, fluorescence, fluorescence lifetime, circular dichroism, and 2D-NMR spectroscopy. The spectral titrations have been performed in aqueous phosphate buffer solution(pH 7.20) at 25°C to give the complex stability constants(KS) and Gibbs free energy changes(-ΔG°) for the inclusion complexation of hosts 2-9 with organic dyes and other thermodynamic parameters(ΔH° and TΔS°) for the inclusion complexation of 2-5 with fluorescent dyes ANS and TNS. The results obtained indicate that β-cyclodextrin dimers 2-5 can coordinate with one or two platinum(IV) ions to form 1:1 or 1:2 stoichiometry metallobridged bis(β-cyclodextrin)s. As compared with parent β-cyclodextrin(1) and bis(β-cyclodextrin)s 2-5, metallobridged bis(β-cyclodextrin)s 6-9 can further switch the original molecular binding ability through the coordinating metal to orientate two β-cyclodextrin cavities and an additional binding site upon the inclusion complexation with model substrates, giving the enhanced binding constants KS for both ANS and TNS. The tether length between two cyclodextrin units plays a crucial role in the molecular recognition with guest dyes. The binding constants for TNS decrease linearly with an increase in the tether length of dimeric β-cyclodextrins. The Gibbs free energy change(-ΔG°) for the unit increment per ethylene is 0.32 kJ mol 1 for TNS. Thermodynamically, the higher complex stabilities of both ANS and TNS upon the inclusion complexation with 2-5 are mainly contributed to the favorable enthalpic gain(-ΔH°) by the cooperative binding of one guest molecule in the closely located two β-cyclodextrin cavities as compared with parent β-cyclodextrin. The molecular binding ability and selectivity of organic dyes by hosts 1-9 are discussed from the viewpoints of the multiple recognition mechanism and the size/shape-fitting relationship between host and guest.

Studies on linear aggregation prepared by inclusion complexation of bridged bis(β-cyclodextrin)s and calix[4]arene derivatives provide a simple method to control linear aggregation compactness by molecular recognition.

Linear biscatechols and triangular triscatechols possessing spacers containing phosphane oxide were synthesized. For this, the central phosphorus was introduced by the reaction of active organometallic intermediates with either dichlorophenylphosphane or phosphorus trichloride/phosphoryl chloride. In the final steps, the methyl ethers at the veratrol units were cleaved by boron tribromide to afford the free phosphane oxide catechol derivatives, which in metal-directed self-assembly processes would lead to helical or tetrahedral supramolecular aggregates.